Thursday, 29 October 2020

Dropping fermentation

A two-stage fermentation, where the process kicked off in a tall cylindrical vessel then the wort was “dropped” to a shallow square vessel, remained fairly popular in the South of England.

There seems to have been quite a bit of variation in exactly how long elapsed between pitching and dropping. At some breweries, such as Fullers and Adnams, the wort remained no more than 12 hours in the upper round.  At others, it could stay there for two or three days.

Fullers brewing logs recorded the fermentation process in some detail:

5th November 1941 Fullers X Ale fermentation
day and time temperature OG action
Wednesday   18:00 63º F 1028.6 pitched
Thursday      03:00     dropped
15:00 64º F 1022.8  
22:00 65.5º F 1019.2  
Friday         6:30     lowered sluices
08:00 68º F 1013.3  
14:30     collected and pumped
15:00 68º F 1010.8  
20:00 68º F 1008.9  
Saturday           8:00 67.5º F 1007.8  
12:00 67º F 1007.5  
20:00 66.5º F 1007.5  
Sunday             9:00     liquor on
Tuesday           4:30 59º F   racked
Fullers brewing record held at the brewery.

The fermenting wort was only briefly in the upper round – a mere 9 hours – before being dropped. “Collected” refers to yeast being skimmed off the top for repitching. While “liquor on” is the attemperator being activated.

All in all, the fermentation took around 12 hours short of a full week. Which seems quite a long time for a beer of such a modest gravity.


Michael Foster said...

Just two and a half days until it gets pretty much at FG. Interesting how homebrewers for years have insisted on 10+ day fermentations when the pros were doing it for much less long ago.

A Brew Rat said...

I usually drop my homebrewed bitters and milds after 18 hours. I have found this increases the fruity esters that I like in a pint of British ale, especially for yeasts like WY1968, WY1469, and the White Labs Burton ale yeast. I don't do this with the bigger hoppier IPAs.

Anonymous said...

Do you have a sense how much oxygen gets into the fermenting beer as it transfers from high to low? I'm curious if they worried about oxidation at that point, or if they were trying to give the yeast a fresh dose of oxygen to encourage activity.

Ron Pattinson said...

A Brew Rat,

now that's interesting. Exactly what sort of vessels do you use?

Ron Pattinson said...


I assume aerating the wort was one of the reasons for dropping.

A Brew Rat said...

Ron, I ferment my ales in 6.5 gallon plastic buckets.

Dropping sometimes also adds a little hint of diacetyl, although not all the time.